1. Field of the Invention
This invention relates to catalysts. In accordance with one aspect, this invention relates to catalysts useful for the disproportionation of olefins. In a further aspect, this invention relates to a process for the conversion of olefins. In another aspect, this invention relates to a process for the disproportionation of olefinic hydrocarbons. In yet another aspect, the invention relates to a method for preparing catalyst.
2. Description of the Prior Art
The disproportionation, or metathesis, of olefins is a reaction in which one or more olefinic compounds are transformed into other olefins of different molecular weights. The disproportionation of an olefin with itself to produce an olefin of a higher molecular weight and an olefin of a lower molecular weight can also be referred to as self-disproportionation. For example, propylene can be disproportionated to ethylene and cis-, and trans-2-butene. Another type of disproportionation involves the cross-disproportionation of two different olefins to form still other olefins. An example would be the reaction of one molecule of 2-butene with one molecule of 3-hexene to produce two molecules of 2-pentene.
By the term "disproportionation" or "metathesis" throughout this specification is meant the conversion of the feed olefinic (or unsaturated) hydrocarbon to a mixture of olefinic (or unsaturated) hydrocarbons having different numbers of carbon atoms than the feed hydrocarbons.
Many catalysts have been developed for disproportionation. For example, those comprising inorganic oxides containing a catalytic amount of a metal or metal oxide have been employed widely for continuous, fixed-bed conversion of olefins.
One such catalyst comprises a silica support and an oxide of tungsten. The present invention is based upon the discovery of a way to improve the activity of such a catalyst.